Thankfully, plenty of people care about proper punctuation/typography. See most of Lynn Truss' books (particularly "Eats, Shoots and Leaves").

My favorite spelling/typographical pet peeve is lack of use of a dieresis. This typographic mark (the name of which sounds unfortunately like some sort of bowel disorder) is used to indicate that two adjacent vowels belong to two different syllables by placing what otherwise looks like an umlaut (two horizontal dots above a letter: ü) above the second vowel.

The names Zoe and Chloe might be pronounced "zoh" and "cloh" (like Cletus did to two of his many children in an episode of The Simpsons) were it not for the occasional parent who names their kids Zoë (ZOH-ee) and Chloë (CLOH-ee). Plenty of other words benefit from use of a dieresis instead of a hyphen (or nothing): coöperate vs. co-operate or cooperate, e.g. Some words look, and sound, funny without a dieresis: preemptive, preeminent,)

Even if you don't want to employ the dieresis, at least now you'll know what it is when you see it (and won't think people are trying to act pretentious by sticking some diacritical marks on their name like some sort of '80s metal band).